Here's some pics of a DIY beer holder I made last season.
It was pretty simple to make:
- Set bottle and koozie on counter. Set sharpie on top of Koozie with tip on bottle and rotate bottle to mark a straight cut line
- Cut along line and cut a small slit near bottom of bottle for a strap
- Drill or cut a few holes in bottom of bottle for drainage
I also tried using a spare water bottle cage, mounted in the same manner as this holder, but with thicker koozies, it's harder to get can in and out. Water bottle cages work fine with thinner, neoprene koozies.
I also got some cheap can toppers (with flip-up lid over drinking hole) from amazon to keep the beer in the can and water out.